From the space exploration vessel Saturnius – which is heading to a destination that never gets any closer - to a doomed planet Earth and beyond, River's journey will bring her closer to a new foe... and an encounter with both the Sixth and Seventh Doctors.

A planetary anomaly. A scientific impossibility. A mystery to be solved.

Of course, River Song expects to be consulted. She expects her valuable knowledge and experience will help the crew of the Saturnius unlock the strange phenomenon that has appeared in Earth’s solar system.

But what River doesn’t expect is a stowaway. An infuriating little man, calling himself the Doctor.